The present invention relates to an apparatus for preventing solidification of molten metal in an electromagnetic pump. In particular, the apparatus according to the present invention is adapted to be used when the molten metal in a container is supplied to molds or the like by means of an electromagnetic pump with the supply of molten metal being intermittently suspended for considerably long time.
In supplying molten metal to a mold by means of an electromagnetic pump mounted on a metal container, the molten metal received in the container is held in high temperature due to the high insulating characteristic of the container itself by actuating the heater provided thereon, thus being prevented from solidifying at least for a certain period.
However, the molten metal in the electromagnetic pump provided on the container will alter into solid state as the temperature thereof is lowered after certain period of suspension in supplying molten metal into the molds or the like, although no problem is caused in the course of continuous supply. This is a matter of natural consequence because the molten metal of unit volume received in the electromagnetic pump must contact with the inner wall surface of lower temperature and of larger area than in the container. Therefore, it was heretofore necessary in the operation of molten metal supply to limit the amount of molten metal in the container to a certain amount of an uninterrupted and exhaustive supply of molten metal. Such manner of supply has caused the inconveniences in the operation of molten metal supply.
To overcome the above mentioned difficulties, it was proposed to inverse the direction of travelling magnetic field in the electromagnetic pump. By inversing the direction of travelling magnetic field, the surface of the molten metal in the electromagnetic pump is lowered in relation to the level of molten metal surface in the container, while the circulation of molten metal is generated as will be explained below.
The driving force in electromagnetic pump to push molten metal into the container is largest in the central portion thereof and is decreased at the both sides thereof by degrees. (This is well known as the lateral edge effect and is substantiated through experiments.) Such distribution of driving force generates the circulation of molten metal wherein the central flow is directed to the container and the side flows are directed to the outlet of the pump. Since the driving force generated by travelling magnetic field is so feeble at the position where the electromagnetic pump is connected to the container, the molten metal around the position of connection fails to be transferred to the full inside of the container and tends to return, that is, to flow upwardly along the both sides of molten metal conduit. (The decrease of driving force at the longitudinal edge is well known as longitudinal edge effect.)
It was found that the above mentioned circulation of molten metal flow functions to check solidification of molten metal to a certain extent, but it was impossible to substantially prevent the drop of molten metal temperature, thus bringing about the defects such as nonuniformity or the inferiority of resulted articles. Summary of the Invention
It is therefore the object of the present invention to keep the molten metal in electromagnetic pump in substantially the same temperature as that in a container in spite of the suspension of molten metal supply, by means of partition walls provided on the molten metal inlet in the electromagnetic pump where the pump is connected to the container. These partition walls serve to continuously exchange the molten metal in the pump with that in the container.
The detailed construction of the apparatus according to the present invention will be explained hereinafter with reference to the accompanied drawings wherein: